A human shoulder articulates about a loose fitting ball-and-socket joint that allows extremely free movement of the arm relative to the body's trunk. The ball is formed on the head of the humerus, and the socket is formed by a shallow laterally opening glenoid cavity of the scapula bone. The depth of the socket is increased by a circumferential ring of fibrocartilage, the glenoid labrum, to which the head of the humerus is attached by an encircling mass of connective tissue called the articular capsule. Such capsule includes, for example, ligaments and tendons.
There is little area of contact between the ball of the humerus and the glenoid cavity. Nevertheless, there is always a considerable part of the ball of the humerus in contact with the articular capsule. The loose fitting ball-and-socket connection allows the articulating surfaces of the bones to be substantially separated. Since this joint is so loosely constructed, it is frequently dislocated in contact sports. Furthermore, recent studies reveal that athletes who engage in throwing or racquet sports can chronically develop shoulder instability by creating a gradual separation between the cartilage labrum and bony glenoid.
A shoulder can become unstable in any one direction, or it can become unstable in all directions i.e., a global instability. There is greater superior (upper) and posterior (rearward) support for the shoulder joint. Therefore, frequent dislocations occur in an anterior (forward) and inferior (downward) direction. In fact, these dislocations account for ninety percent of shoulder instabilities. An instability can be created by an avulsion (or tearing away) of the glenoid labrum from the superior margins of the glenoid cavity of the glenohumeral joint. From an anterior to posterior direction this capsulolabral separation is known as a SLAP (superior labrum, anterior to posterior) lesion. In other words, a SLAP lesion is an avulsion of the cartilage rim from the superior region of the socket extending posteriorly and anteriorly. A Bankart lesion, which is an avulsion of the glenoid labrum from the anterior and inferior margins of the glenoid cavity, and a rotator cuff lesion, which is an avulsion of the tendon from the humeral head are also common injuries associated with the shoulder joint, and can be a secondary result of superior shoulder instability.
As a result of the anterior shoulder injuries described above, surgical repair of the glenoid labrum is usually required to regain shoulder stability. The standard of care known in the art for many years has been by open shoulder surgery methods and typically involved spreading the muscles overlying the anterior side of the joint and severing some of the connective tissue to provide access to the anterior glenoid rim. In one technique, intersecting holes are drilled in the anterior and lateral faces of the glenoid cavity adjacent to the rim for attaching sutures that secure the detached labrum firmly to the glenoid rim at two or three locations. Over time the labrum re-attaches. Unfortunately, as with most open surgery techniques, morbidity of the repair site can and does frequently occur, resulting in a prolonged healing process.
Arthroscopic surgery can be used to repair a number of gleno-humeral injuries. Repair of the superior glenoid labrum becomes one of the most challenging surgical procedures in all of shoulder surgery. The superior aspect of the glenoid is bounded superiorly by the rotator cuff, which must not be violated. Anteriorly, the biceps tendon conflicts with an anterior superior approach to the superior labrum, and secondary inflammatory reaction caused by an unstable labrum can interfere with the view through the arthroscope.
Abrading the glenoid rim during arthroscopic surgery is essential to create a “healing bed” for the labrum. Nevertheless, different and more invasive techniques for securing the labrum to the glenoid rim area are available. In one technique, one or more staples are used to connect the glenoid labrum to the anterior side of the scapular neck medially of the glenoid cavity. In another technique, the labrum is impaled with a rivet that is driven into the scapular neck. In another technique, blind bores are drilled adjacent to the anterior glenoid rim for specially designed suture anchors. In yet another technique, a hole is drilled through the scapular neck for pin or screw placement to which suture material can be attached, and which is then used to tie the glenoid labrum to the scapular neck.
Although arthroscopic techniques are a great improvement over open shoulder surgery, there remains room for improvement. For example, a problem in arthroscopic glenoid labrum re-attachment is positioning the drilling and securing devices in a fast and efficient manner with minimal trauma to the surrounding tissue. Significant tissue damage can occur from repeated unsuccessful attempts to blindly locate a proper or desired re-attachment site. This surgical site could be as much as four to eight inches (10.16 cm to 20.32 cm) deep from the skin surface depending upon the size and muscular development of the patient. Prior art instruments used to aid locating connective tissue re-attachment sites are known in the art, but are designed for the particular environment found in the knee for anterior and posterior cruciate ligament reconstruction. See generally, U.S. Pat. Nos. 5,269,786; 5,112,337; and 4,920,958. Habermeyer (U.S. Pat. No. 5,575,801) shows an apparatus for arthroscopic rotator cuff repair, but the Habermeyer device does not include a method or device suited for accurate site selection for the re-attachment of the glenoid labrum to the glenoid cavity.
Thus, there is a desire and a need for a device and method to improve site selection and suture placement as required in the repair of lesions of the glenoid labrum to the glenoid cavity in a shoulder, specifically a SLAP lesion repair.